SpecFitWhat 17-140 means on your glasses
You found a stamp inside a temple arm, but only part of it was legible: 17-140. That is not the full size. It is the bridge width and the temple length, in millimetres. Here is what those two numbers tell you, and what they leave out.
Where 17-140 sits in the full stamp
A complete size stamp reads lens width, then bridge width, then temple length: for example 54□17 140. The square marks the boxing system, the standard way lens width is measured. 17-140 is the last two numbers of that stamp. It skips the lens width. The lens width may have worn off, or it may be stamped on the other arm.
Read in full, 17-140 means a 17 mm bridge and a 140 mm temple. Neither number tells you the frame's overall width on its own. For that you need the lens width too, which is explained in full in what the numbers on your glasses mean.
17 mm bridge: who it suits
Bridge width is the gap between the lenses, measured across your nose. The typical range is 14 to 24 mm, and 17 mm sits in the middle of it. That makes it a medium bridge, built for an average nose.
If your nose is narrower or your bridge sits low, a 17 mm gap can still leave the frame resting too low, and a bridge under about 16 mm usually sits better. If your nose is wider, 17 mm can pinch, and 19 mm or more usually feels right. Red marks beside your nose after wear mean the bridge is too narrow. A frame that keeps sliding down means it is too wide.
140 mm temple: who it suits
Temple length runs from the hinge to the tip of the arm. 140 mm is the most common length made for adult frames, and it reaches the ear on most adult heads. The typical range across all frames is 120 to 150 mm, but most adults wear somewhere between 135 and 145 mm.
A 140 mm arm should run straight back and bend down just past the top of your ear. Smaller heads often do better with 135 mm. Larger heads often want 145 mm or more. If a frame's temples are the right shape but slightly off in length, an optician can usually move the bend point by a few millimetres.
What full stamps containing 17-140 look like
Because 17-140 leaves out lens width, the same bridge and temple numbers appear on frames of very different overall sizes. The table below shows common lens widths paired with a 17 mm bridge and 140 mm temple, and the total frame width each one produces.
| Full stamp | Estimated total width | Suits a face width of about |
|---|---|---|
| 50□17 140 | 129 mm | 127 to 132 mm |
| 52□17 140 | 133 mm | 131 to 136 mm |
| 54□17 140 | 137 mm | 135 to 140 mm |
| 56□17 140 | 141 mm | 139 to 144 mm |
Total width is estimated as two lens widths, plus the bridge, plus about 12 mm for the hinges. A frame fits when its total width sits within 2 to 3 mm of your face width, measured temple to temple. That is why a full stamp matters more than the bridge and temple alone: the same 17-140 can belong to a frame that fits a narrow face or one that fits a wide face.
Other numbers a stamp can carry
Some stamps add a fourth number after the temple length, for lens height. That matters mainly for progressive lenses, where enough height is needed for the reading zone. A stamp can also carry a colour code or a model name near the size numbers. Those are not measurements, and you can ignore them when checking fit.
Even a full stamp does not describe everything. Two frames with identical numbers can still fit differently, because the numbers say nothing about the frame's shape, its wrap, its weight, or how the nose pads sit. Numbers narrow the search. Trying the frame, or checking it against your own measured face, decides it.
SpecFit reads a frame's full size stamp and checks it against your measured face. SpecFit scans your face with the iPhone depth camera and measures your PD, face width, and bridge width in real millimetres, accurate to about ±1 mm. Paste a link to any glasses and the app reads the listing's size stamp and scores the fit against your face. The fit check is free. Rendering the frame on your face costs one credit.
Questions
What does 17-140 mean on glasses?
17 is the bridge width in millimetres, the gap between the lenses across your nose. 140 is the temple length in millimetres, the arm from hinge to tip. They are the last two numbers of a full stamp such as 54-17-140. The lens width is printed separately.
Is a 17 mm bridge narrow or wide?
Medium. The typical range is 14 to 24 mm. Below about 16 mm suits a narrower nose, 19 mm and above suits a wider one, and 17 mm suits an average nose.
Will 140 mm temples fit my head?
Most likely. 140 mm is the most common adult temple length. Smaller heads often prefer 135 mm and larger heads 145 mm or more, and an optician can adjust the bend by a few millimetres.
I only see 17-140. Where is the lens width?
Check the other temple arm and behind the bridge. It is often stamped separately, just before the square symbol: something like 54, then the square, then 17 140.